Rubber linings in abrasive-material handling equipment such as centrifugal pumps for dredging sand, mud and for pumping slurry are old. The use of such liners is normally for purpose of economy and to enable quick replacement when worn beyond a certain point. Formerly, either no liners were used for dredging or pumping the foregoing materials or cast alloy iron or steel liners were used. Rubber was found to be much more economical, when pumping clean, abrasive sand. However, where the material being pumped or dredged included sharp rocks, broken glass, tin cans, pieces of metal and other sharp hard particles found in trash as may accumulate in the beds of canals, rivers, harbors and other bodies of water, the use of rubber wear components in the centrifugal dredges has been found to be valueless, because the sharp objects remove large pieces of the rubber.
Also, heretofore, rubber liners have been used as impact receiving wear components in hoppers, chutes, and the like to resist the wear due to rocks and the like that are handled, but such liners are not used where the angle of impact is less than forty degrees and the rate of movement of the material thereover is greater than twenty feet per second, due to greatly accelerated wear where these limits are exceeded. Such liners are specially formed to present surfaces having angles of impact as close to ninety degrees as possible to enable the resiliency of the relatively soft rubber to absorb much of the shock free from the shearing effect of a low angle of impact.
Liners in centrifugal dredge and slurry pumps have heretofore been manufactured to provide continuous volute portions circumferentially around the impeller, and continuous door or side walls, although they and the casing may be split in the plane of the volute for insertion and removal of the liners. In either instance the wear is not uniform but occurs in different areas. To extend the life of the costly metal liners, an expensive and time consuming expedient is adopted for building up the worn areas with welding, and applying hard faced welding surfaces. Otherwise the liners are replaced, although extensive areas of the wear surfaces show little wear.
The side or door liners show wear in many instances between the runner-shrouds or discs and the liners adjacent thereto due to movement of the water and abrasive material from the volute portion across the faces of said liners and the inlet under the influence of the high pressure differential between said portion and the inlet portion, the pressure at the latter being negative. This wear across the liners progressively reduces the efficiency of the pump as the wear increases, with a resultant rise in the operation costs. Here again, in the case of the metal liners, resort is made to building up the worn areas with welding.
In the liners hereinafter shown and described, each comprises a layer of rubber or rubber-like material in which the wear surface is smooth. When used hereafter in this application, the term "rubber" shall mean any natural or synthetic, resilient, rubber-like material. Embedded in the rubber layer is one or more sheets of high carbon steel wire mesh material or other tough, abrasive resistant mesh, the wire of which is substantially inseparably bonded or vulcanized to the rubber. This sheet, or sheets where more than one is used, is or are parallel with said wear surface, and in the latter instance the sheets are spaced apart.
The size of the wire and the mesh openings are such as to resist breakage from the impact and abrasion of the materials being dredged, such as hard rocks, broken glass including glass bottles, tin cans, wire, pieces of metal etc. The wire defining the mesh openings protects the rubber therein and prevents the deepening of any areas worn to the sheet and also checks the expansion of such areas. Thus, the mesh sheets provide abrasion resistant wear surfaces.
Where the liners are in hoppers, chutes and the like that take the impact of rocks, aggregate and the like, fed thereto and over which such material is moved, the liners are not necessarily in sections in each installation, and they usually are fairly accessible for installation, removal and replacement. The wear surfaces are smooth thereby offering no unusual resistance to fast movement of the materials thereover, and the angle of impact may be thirty degrees and less to expedite such movement. The liners are of rubber, have the wire mesh sheet or sheets embedded therein and bonded thereto, to provide a lining material having the long wear characteristic of hard alloy metals but at a fraction of the cost.